Linear actuator

Abstract

At least a rotor fixing portion and a bearing fitting portion are combined to form a hollow rotary shaft. The rotor of a rotary motor portion is fixed on the rotor fixing portion. A thrust radial bearing is fitted on the outer periphery of the bearing fitting portion and a screw nut is fitted to the bearing fitting portion. The rotor fixing portion and the bearing fitting portion are coupled with screw member(s) which are inserted into the hollow rotary shaft from one axial end of the hollow rotary shaft and axially extend inside the bearing fitting portion and the rotor fixing portion. A flange portion of the screw nut is fixed on an abutment portion of the bearing fitting portion in abutment with an end surface of an inner race of the thrust radial bearing that is located on the one axial end side.

What is claimed is: 
     
       1. A linear actuator comprising:
 a rotary motor portion including: 
 a rotor; and 
 a hollow rotary shaft formed by combining at least:
 a rotor fixing portion on which the rotor is fixed; and 
 a bearing fitting portion; 
 
 an output screw shaft disposed coaxially with the hollow rotary shaft and operable to move inside the hollow rotary shaft; 
 a screw nut fixed to the bearing fitting portion and including:
 a screw portion located inside the hollow rotary shaft and screwed onto the output screw shaft; and 
 a flange portion unitarily formed with the screw portion and projecting radially outwardly from one axial end of the hollow rotary shaft; 
 
 a thrust radial bearing including an inner race and an outer race and operable to rotatably support the hollow rotary shaft on the one axial end side, the thrust radial bearing being fitted on an outer periphery of the bearing fitting portion of the hollow rotary shaft, wherein: 
 the rotor fixing portion and the bearing fitting portion are coupled with one or more screw members which are inserted into the hollow rotary shaft from the one axial end and axially extend inside the bearing fitting portion and the rotor fixing portion; 
 the bearing fitting portion is unitarily formed with an abutment portion which abuts onto an end surface of the inner race of the thrust radial bearing that is located on the one axial end side; and 
 the flange portion of the screw nut is fixed on the abutment portion of the bearing fitting portion. 
 
     
     
       2. The linear actuator according to  claim 1 , wherein:
 the rotor fixing portion is unitarily formed with an abutment portion which abuts onto an end surface of the inner race of the thrust radial bearing that is opposite to the end surface located on the one axial end side. 
 
     
     
       3. The linear actuator according to  claim 1 , further comprising a joint member disposed between the rotor fixing portion and the bearing fitting portion, wherein:
 the joint member includes:
 a first fitting concave portion fitted with an end of the rotor fixing portion that is located on the one axial end side; 
 a second fitting concave portion fitted with an end of the bearing fitting portion that is located on an opposite side to the one axial end side; and 
 a partition portion located between the rotor fixing portion fitted in the first fitting concave portion and the bearing fitting portion fitted in the second fitting concave portion; and 
 
 the one or more screw members axially extend inside the bearing fitting portion, the partition portion of the joint member, and the rotor fixing portion to couple the bearing fitting portion, the joint member, and the rotor fixing portion. 
 
     
     
       4. The linear actuator according to  claim 3 , wherein
 the joint member is unitarily formed with an abutment portion which abuts onto an end surface of the inner race of the thrust radial bearing that is opposite to the end surface located on the one axial end side. 
 
     
     
       5. The linear actuator according to  claim 1 , wherein:
 the rotary motor portion includes:
 a stator portion constituted from a stator core and a winding portion attached to the stator core; and 
 a rotor portion fixed to the rotor fixing portion; and 
 
 the linear actuator further includes:
 a first end bracket fitted with an end of the stator core that is located on an opposite side to the one axial end side; 
 an intermediate bracket fitted with an end of the stator core that is located on the one axial end side and is also fitted with the outer race of the thrust radial bearing, the intermediate bracket having a first abutment portion and a second abutment portion formed therein, the first abutment portion abutting onto an end surface of the outer race of the thrust radial bearing that is located on the opposite side to the one axial end side, and the second abutment portion abutting onto a bearing retaining plate in abutment with an end surface of the outer race of the thrust radial bearing that is located on the one axial end side; and 
 a second end bracket fitted with an end of the intermediate bracket that is located on the one axial end side, with the output screw shaft penetrating therethrough. 
 
 
     
     
       6. The linear actuator according to  claim 1 , wherein:
 the rotary motor portion includes:
 a stator portion constituted from a stator core and a winding portion attached to the stator core; and 
 a rotor portion fixed to the rotor fixing portion; and 
 
 the linear actuator further includes:
 a first end bracket fitted with an end of the stator core that is located on an opposite side to the one axial end side; 
 an intermediate bracket fitted with an end of the stator core that is located on the one axial end side and is also fitted with the outer race of the thrust radial bearing, the intermediate bracket having a first abutment portion and a second abutment portion formed therein, the first abutment portion abutting onto an end surface of the outer race of the thrust radial bearing that is located on the opposite side to the one axial end side, and the second abutment portion abutting onto a bearing retaining plate in abutment with an end surface of the outer race of the thrust radial bearing that is located on the one axial end side; and 
 a second end bracket fitted with an end of the intermediate bracket that is located on the one axial end side, with the output screw shaft penetrating therethrough; and 
 
 a fitted portion including a reference surface in contact with an inner peripheral surface of the stator core is unitarily formed with an end of the intermediate bracket that is located on the opposite side to the one axial end side. 
 
     
     
       7. The linear actuator according to  claim 2 , wherein:
 the rotary motor portion includes:
 a stator portion constituted from a stator core and a winding portion attached to the stator core; and 
 a rotor portion fixed to the rotor fixing portion; and 
 
 the linear actuator further includes:
 a first end bracket fitted with an end of the stator core that is located on an opposite side to the one axial end side; 
 an intermediate bracket fitted with an end of the stator core that is located on the one axial end side and is also fitted with the outer race of the thrust radial bearing, the intermediate bracket having a first abutment portion and a second abutment portion formed therein, the first abutment portion abutting onto an end surface of the outer race of the thrust radial bearing that is located on the opposite side to the one axial end side, and the second abutment portion abutting onto a bearing retaining plate in abutment with an end surface of the outer race of the thrust radial bearing that is located on the one axial end side; and 
 a second end bracket fitted with an end of the intermediate bracket that is located on the one axial end side, with the output screw shaft penetrating therethrough. 
 
 
     
     
       8. The linear actuator according to  claim 2 , wherein:
 the rotary motor portion includes:
 a stator portion constituted from a stator core and a winding portion attached to the stator core; and 
 a rotor portion fixed to the rotor fixing portion; and 
 
 the linear actuator further includes:
 a first end bracket fitted with an end of the stator core that is located on an opposite side to the one axial end side; 
 an intermediate bracket fitted with an end of the stator core that is located on the one axial end side and is also fitted with the outer race of the thrust radial bearing, the intermediate bracket having a first abutment portion and a second abutment portion formed therein, the first abutment portion abutting onto an end surface of the outer race of the thrust radial bearing that is located on the opposite side to the one axial end side, and the second abutment portion abutting onto a bearing retaining plate in abutment with an end surface of the outer race of the thrust radial bearing that is located on the one axial end side; and 
 a second end bracket fitted with an end of the intermediate bracket that is located on the one axial end side, with the output screw shaft penetrating therethrough; and 
 
 a fitted portion including a reference surface in contact with an inner peripheral surface of the stator core is unitarily formed with an end of the intermediate bracket that is located on the opposite side to the one axial end side. 
 
     
     
       9. The linear actuator according to  claim 3 , wherein:
 the rotary motor portion includes:
 a stator portion constituted from a stator core and a winding portion attached to the stator core; and 
 a rotor portion fixed to the rotor fixing portion; and 
 
 the linear actuator further includes:
 a first end bracket fitted with an end of the stator core that is located on an opposite side to the one axial end side; 
 an intermediate bracket fitted with an end of the stator core that is located on the one axial end side and is also fitted with the outer race of the thrust radial bearing, the intermediate bracket having a first abutment portion and a second abutment portion formed therein, the first abutment portion abutting onto an end surface of the outer race of the thrust radial bearing that is located on the opposite side to the one axial end side, and the second abutment portion abutting onto a bearing retaining plate in abutment with an end surface of the outer race of the thrust radial bearing that is located on the one axial end side; and 
 a second end bracket fitted with an end of the intermediate bracket that is located on the one axial end side, with the output screw shaft penetrating therethrough. 
 
 
     
     
       10. The linear actuator according to  claim 3 , wherein:
 the rotary motor portion includes:
 a stator portion constituted from a stator core and a winding portion attached to the stator core; and 
 a rotor portion fixed to the rotor fixing portion; and 
 
 the linear actuator further includes:
 a first end bracket fitted with an end of the stator core that is located on an opposite side to the one axial end side; 
 an intermediate bracket fitted with an end of the stator core that is located on the one axial end side and is also fitted with the outer race of the thrust radial bearing, the intermediate bracket having a first abutment portion and a second abutment portion formed therein, the first abutment portion abutting onto an end surface of the outer race of the thrust radial bearing that is located on the opposite side to the one axial end side, and the second abutment portion abutting onto a bearing retaining plate in abutment with an end surface of the outer race of the thrust radial bearing that is located on the one axial end side; and 
 a second end bracket fitted with an end of the intermediate bracket that is located on the one axial end side, with the output screw shaft penetrating therethrough; and 
 a fitted portion including a reference surface in contact with an inner peripheral surface of the stator core is unitarily formed with an end of the intermediate bracket that is located on the opposite side to the one axial end side. 
 
 
     
     
       11. The linear actuator according to  claim 4 , wherein:
 the rotary motor portion includes:
 a stator portion constituted from a stator core and a winding portion attached to the stator core; and 
 a rotor portion fixed to the rotor fixing portion; and 
 
 the linear actuator further includes:
 a first end bracket fitted with an end of the stator core that is located on an opposite side to the one axial end side; 
 an intermediate bracket fitted with an end of the stator core that is located on the one axial end side and is also fitted with the outer race of the thrust radial bearing, the intermediate bracket having a first abutment portion and a second abutment portion formed therein, the first abutment portion abutting onto an end surface of the outer race of the thrust radial bearing that is located on the opposite side to the one axial end side, and the second abutment portion abutting onto a bearing retaining plate in abutment with an end surface of the outer race of the thrust radial bearing that is located on the one axial end side; and 
 a second end bracket fitted with an end of the intermediate bracket that is located on the one axial end side, with the output screw shaft penetrating therethrough. 
 
 
     
     
       12. The linear actuator according to  claim 4 , wherein:
 the rotary motor portion includes:
 a stator portion constituted from a stator core and a winding portion attached to the stator core; and 
 a rotor portion fixed to the rotor fixing portion; and 
 
 the linear actuator further includes:
 a first end bracket fitted with an end of the stator core that is located on an opposite side to the one axial end side; 
 an intermediate bracket fitted with an end of the stator core that is located on the one axial end side and is also fitted with the outer race of the thrust radial bearing, the intermediate bracket having a first abutment portion and a second abutment portion formed therein, the first abutment portion abutting onto an end surface of the outer race of the thrust radial bearing that is located on the opposite side to the one axial end side, and the second abutment portion abutting onto a bearing retaining plate in abutment with an end surface of the outer race of the thrust radial bearing that is located on the one axial end side; and 
 a second end bracket fitted with an end of the intermediate bracket that is located on the one axial end side, with the output screw shaft penetrating therethrough; and 
 
 a fitted portion including a reference surface in contact with an inner peripheral surface of the stator core is unitarily formed with an end of the intermediate bracket that is located on the opposite side to the one axial end side.